High voltage field-effect transistors having high breakdown voltage and low on-state resistance are used in, for example, power management products. Such high voltage field-effect transistors include lateral double-diffused (LD) transistors. The performance of the LD transistors depends on the drain-to-source on-resistance (Rdson) as well as breakdown voltage. For example, low Rdson results in high switching speed while high breakdown voltage (BVdss) increases reliability.
High breakdown voltage may be achieved by increasing the device pitch. For example, an expanded drain region may be provided along the surface of the substrate, increasing the drain-to-gate surface area on the substrate. The higher the desired breakdown voltage, the larger the expanded drain region or larger the drain-to-gate surface area on the substrate. This however increases gate-to-drain capacitance, resulting in a larger Rdson which negatively impacts the switching speed of the transistor. As such, conventional LD transistors achieve a high breakdown voltage by sacrificing switching speed.
The disclosure is directed to transistors with fast switching speed and high breakdown voltage.